Video codecs, such as H.264 codecs and High Efficiency Video Coding (HEVC) codecs are used to compress the amount of video data (e.g., sequence of frames) transmitted between computing devices (e.g., personal computer, smart phone, tablet and the like). Codecs utilize various compression techniques (e.g., integer transforms, inter-frame prediction and intra-frame prediction) to remove information which is not considered to be critical to the viewing of the video, such as quantization of high frequency information and low pass filtering of the chrominance to a spectrum level less than that of the luminance. The reduced data bandwidth allows more requests to be serviced over established pipelines with lower operator costs.
Some conventional compression techniques compress the video signals using chrominance subsampling. For example, chrominance subsampling is typically used for generalized video encoding in which the chrominance is filtered to a lower spectral level without visual impact degradation. Chrominance subsampling seeks to reduce the data bandwidth while maintaining a level of visual quality (i.e., quality as perceived by a viewer of the displayed video) by utilizing a lower visual sensitivity to color transition than brightness transition by the human vision system. During video conferencing, each video signal (i.e., YCrCb signal) in a video stream is divided into a luminance component Y and two color difference (i.e., chrominance components Cr and Cb). Because the human visual system is more sensitive to variations in brightness than variations in color, chrominance subsampling devotes more bandwidth to the luminance component Y than the chrominance components Cb and Cr in each video signal, thereby decreasing the data bandwidth while maintaining a level of visual quality. The resulting video is commonly described as 4:2:0 (½ by ½) or 4:2:2 (½ by 1).
While these conventional techniques typically work well for video in which the chrominance is heavily filtered, they are less suited for transmitted images having sharp image edges, which occur, for example, during remote video conferencing, where computer generated content (drawings, pdfs, spreadsheets, etc.) is encoded and transmitted. The content, which is natively drawn in a 4:4:4 format (albeit RGB) when created, typically results in sharp visual edges. The sharp edges imply high frequency components, however, which are removed in the color channel via subsampling the chrominance, resulting in color bleeding across edges in the image, creating blurriness and false color artifacts.